The amnion develops around the embryo during the second week following fertilization. This is the second membrane to appear after the placenta forms around the chorion. The margin of the amnion is attached to the periphery of the embryonic disk. Eventually, as the embryo grows, the amnion fuses with the chorion surrounding it, and the two membranes become a single amniochorionic membrane. Amniotic fluid fills the amniochorionic membrane to provide a watery environment to protect the growing embryo.
Ordinarily the amniochorionic membrane acts as a primary barrier to bacteria and other potentially damaging organisms by providing a protected, substantially sealed environment throughout the development of the embryo until it ruptures subsequent to the onset of labor. However, this environment is occasionally compromised when it is prematurely ruptured prior to the onset of labor. Technically, premature rupture of the membrane can occur at any time during the forty weeks of gestation. Although definitions vary, "premature rupture of the membrane" refers to rupture of the amniochorionic membrane prior to the onset of labor at any time. In either case, a ruptured membrane poses a considerable risk of infection to both mother and fetus.
Occasionally, rupturing of the membrane follows invasive techniques such as amniocentesis and may lead to infection of the developing fetus. This rupture occurs in about 1 out of every 200 procedures. For women undergoing an amniocentesis in the second trimester, detection of a rupture of the membrane is critical. A gross rupture of fluid could be potentially catastrophic for the developing fetus, as adequate amniotic fluid is a necessity to assure proper lung development, especially prior to 23 weeks.
Beyond the obvious compromise of the membrane caused by amniocentesis, the exact cause of premature rupture is not known. Possible causes include infection, cervical incompetence, and decreased strength of the membrane. Regardless of the cause, with the premature rupture of the membrane, the fetus must be promptly delivered when the mother becomes clinically infected or the fetus shows signs of potential compromise. In either situation, if left untreated, possible death to the fetus and the mother could result. It is noteworthy that chorioamnionitis is present in about 5 to 10 percent of all deliveries and, significantly, is the reason for about 10 percent of all perinatal deaths.
In the event of premature rupture of the membrane, the timing for the delivery of the baby becomes critical, as the risk of intrauterine infection increases significantly as more time passes following rupture. Accordingly, it becomes critical to provide a method of early detection of rupture. The problem is that leaking amniotic fluid--the telltale sign of rupture--is frequently confused by the mother with her own urine or vaginal discharge. (The leakage of urine during pregnancy [particularly during the latter stages] is frequently due to increased pressure on the bladder, thus adding to the overall incidence of false positives.) This results in many false alarms and unnecessary trips to either the doctor's office or to the hospital for evaluation of the pregnant woman to rule out possible rupture of the membrane. These trips lead to wasted time and energy on the part of both the patient and the physician as well as considerable expense to the health care system. A hospital audit revealed an average cost of $250.00 per visit to rule out rupture of the membrane.
Once the pregnant woman identifies leakage, today she has no practical choice but to visit her physician. Because the presence of leaking urine is fleeting, the attending physician must undertake one or more tests in the office to determine whether or not there has been a rupture of the membrane. The conventional test is for the physician to observe the cervix after employing a speculum in an effort to identify pooling of fluid behind the cervix. The physician then applies a swab of pH paper held by a forceps to the fluid located in the area of the cervix to determine whether or not amniotic fluid is present by observing a change in color. Amniotic fluid is alkaline and the pH paper reacts to its presence by turning purple-blue. In addition, the physician may examine a slide on which fluid from the posterior portion of the vagina has been placed and allowed to dry. Amniotic fluid has a very characteristic appearance when dry, called "ferning", and, when the pattern is present, can rule in the rupture of membranes. This determination can assist the physician greatly in evaluating the patient. While functional, experience shows that this examination is far more often than not unnecessary, as the etiology of the fluid is typically due to a cause other than ruptured membranes, i.e., urine, physiologic discharge, etc. The known test is also impractical, leading to particular discomfort for the patient and lost time for the physician.
A variety of in-office or in-hospital tests for the presence of amniotic fluid are known. For example, in U.S. Pat. No. 4,357,945, issued on Nov. 9, 1982 to Janko for DEVICE FOR TESTING AND RUPTURING AMNIOTIC MEMBRANE, a finger-mounted medical testing device is disclosed which tests the intactness of the amniotic membrane. The device of Janko is provided with a pH-responsive material. Upon insertion into the cervix, the indicator material is exposed to the local environment. In U.S. Pat. No. 5,425,377, issued on Jun. 20, 1995 to Caillouette for PH MEASUREMENT OF BODY FLUID, a swab is provided which includes a pH indicator for measuring the pH of vaginal moisture.
Other techniques for use in-office or in-hospital are provided in: U.S. Pat. No. 5,281,522 issued on Jan. 25, 1994 to Senyei et al. for REAGENTS AND KITS FOR DETERMINATION OF FETAL FIBRONECTIN IN A VAGINAL SAMPLE; U.S. Pat. No. 5,096,830, issued on Mar. 17, 1992 to Senyei et al. for PRETERM LABOR AND MEMBRANE RUPTURE TEST; and U.S. Pat. No. 5,554,504, issued on Sep. 10, 1996 to Rutanen for DIAGNOSTIC METHOD FOR DETECTING THE RUPTURE OF FETAL MEMBRANES.
While these various methods provide approaches to testing for amniotic fluid, they do not overcome the basic problem of requiring a professional medical technician to deal in-office or in-hospital with the administration of relevant tests. Further complicating the scenario is the fact that a ruptured amniotic membrane may lead to only a temporary leakage of amniotic fluid, with another leaking episode to occur at a later time. In the meantime, the patient may become infected, with the potential result of great injury to both the baby and the mother.
It is therefore an object of the present invention to overcome the disadvantages associated with known techniques for identifying leaking amniotic fluid and possible rupture of the amniochorionic membrane.
It is a further object of the present invention to provide an article which allows the early identification of the discharge of amniotic fluid without the necessity of a visit to a doctor's office or a hospital.
It is still another object of the present invention to provide such an article which may provide direct evidence of fluid, thus allowing the fluid to be examined microscopially which could lead to a more accurate diagnosis if presentation to a doctor's office or hospital is made.
Yet another object of the present invention is to provide such an article which may be used with minimal inconvenience to the user.
Still a further object of the present invention is to provide such an article which is worn like a sanitary napkin or pad and which may also provide the function of such sanitary items.
Finally, in these times of cost containment, the potential savings from a device which could eliminate unnecessary visits to the physician's office or to the hospital could be tremendous. Thus an additional object of the present invention is to provide such an article which can minimize false positives and have a substantial impact on and impart an economic benefit to the health care system.